Point and signal control system for railways and the like



July 14, 1942. c. F. D. VENNING .,POINT AND SIGNAL CONTROLSYSTEM FORRAILWAYS AND THE LIKE Filled Nov. 22, 1940 ATTORNEY Patented July 14',1942 POINT AND SIGNAL CONTROL SYSTEM FOR RAILWAYS AND THE LIKE CharlesFrancis Dickson Venning, London, England, assigner, by mesneassignments, to The UnienSW-itch and Signal Company, Swiss-vale,

Pa., a corporation of Pennsylvania Application November 22, 1940, SerialNo. 366,777 In Great Britain January 14, 1939 8 Claims.

This invention relates to point and signal control systems for railwaysand the like, and has for its object to provide certain improvements insystems of this character relating to the control of approach locking ofa route controlled by a signal or signals.

This application is a continuation in part of my copending applicationfor Letters Patent of the United States, Serial No. 315,549, filedJanuary 25, 1940, for Point and signal control systems for railways andthe like.

It is usual to provide arrangements for approach locking which preventspoints, that is, track switches, in a route governed by a signal frombeing operated from one position to the other if a train or vehicle ispresent in the section of the track leading to the signal concerned, andthe signal is, or has been, cleared and the associated signal or routelever or control equivalent has been placed in the clear position. Incases in which this signal is arranged to be automatically set to dangerby the passing of a train or vehicle into the section controlling thesignal, the approach locking may be controlled by arelay which isenergized so long as the signal is at danger and when thus energizedeffects the release of the approach locking. The resetting of the signalto clear after a train or vehicle has left the section controlling thesignal, is arranged to restore the .approach locking conditions whichbecome eiT-ective upon the approach of a train or vehicle as abovedescribed. Approach locking control schemes of this type are shown anddescribed in United States Patent No. 1,822,- 218, granted September 8,1931, to Arthur P. Jackel, for Railway traiiic controlling apparatus,and in United States Patent No. 2,211,522, granted August 13, 1940,to'Lester E. Spray, for Multiple control apparatus.

In order to prevent the signal from being automatically re-set to clearafter the 4passage of a train as above described, the automatic settingof the signal to danger is effected by a disengaging relay which isde-energized when the train enters the section controlling the signaland can only be re-energized when the signal or route lever/or itsequivalent is manually operated to the danger or normal positiontemporarily after the passage of 'the train. Relays t2 and t3,

shown in Figj of the Spray patent already re- In such cases it is usualfor the approach locking to be released by the energization of -afurther relay, the pick-up circuit of which is only energized when thesignal is at danger and either the approach section is unoccupied or thedisengaging relay is cle-energized, this further relay being providedwith a stick circuit completed so long as the signal remains at dangenThe disengaging relay de-energized is employed in this approach lockingcircuit to prevent the continuance of the approach locking 'by a secondtrain or vehicle approaching the signal at danger, after the first trainor vehicle has passed out of the section governed by the signal and thesignal or route lever or equivalent has not been restored to its normalposition before the second train or vehicle has occupied the approachlocking track circuits. Relay RMR, shown in the Vantassel patent alreadyreferred to, is controlled in this Way by relay TS for releasing theapproach locking. In the Spray patent already mentioned, relay PI shownin Fig. l could be controlled in this way by substituting a contact ofrelay t2 for contact |62T2.

In the case, however, of a signal provided with approach locking andbeing controlled independently of track circuits, that is to say, beingset to its danger or clear position otherwise than automatically by thepassage of a train or vehicle, the relay arrangement above describedcannot be employed since a disengaging relay, if utilized, might becomepermanently de-energized owing to a broken wire for example, and theapproach locking become permanently released while the signal is in theclear as well as the danger position. If, for instance, signal Sla shownin the Spray patent were controlled to remain in the clear position eventhough relay t2, if a contact of this relay were substituted for contactH'SZTZ, remains dre-energized, relay Pl would remain energized eventhough signal Sla were clear and a train were approaching this signal insection a--A while relay t2 is falsely die-energized due to a brokenwire in its pickup circuit.

According to the present invention in which the signal provided withapproach locking is controlled independently of track circuits, anapproach locking relase relay is provided which is arranged when in itsenergized position to eect the release of the approach locking providingthat the signal is at"danger, this relay being normally de-energizedwhen the signal or route lever or its equivaient is in the normalposition for no traffic along the route and only re-energized when thesignal or route lever or its equivalent is in the reverse position and aselected track circuit beyond the signal is occupied.

Any failure in the circuits for the relay IAN S will thus prevent theapproach locking from being released, thereby ensuring safety inoperation.

The invention is particularly applicable to systems in which points ortrack switches are arranged to be controlled by route setting andlocking relays comprising normal and reverse solenoids, which in turncause to operate point or switch setting and locking relays to therequired positions to effect the operation of the track points orswitches in the route to which a route setting and locking relay appliesand which relay remains locked in the position to which it was last setuntil the opposite solenoid is energized.

A relay of this type, designatedas electrically operated switchmechanism, is shown and described in Unit-ed States Patent No.2,164,822, granted July 4, 1939, to Arthur G. Kershaw and Norman G.Kershaw.

The invention is illustrated by way of example in the accompanyingdrawing of which Figure 1 is a diagrammatic representation of a stretchof railway track comprising a number of routes. Figure 1 also showstypical operating and indication circuits for one of the switches in thestretch of railway track, and shows energizing circuits for a signal forone of the routes. Figure 2' is a diagram of connections illustrating inconventional form the control of the signal for one of the routes shownin Figure 1.

Figures 3 and 4 are diagrams similar to Figure 2, illustratingrespectively the control of the approach locking release relay providedin accordance with the invention and the control of the route settingand locking relay for one of the routes with which the signal of Figures1 and 2 is associated. Figure 4 also shows the control of the point orswitch setting and locking relay for one of the track switches in theroute with which the signal of Figures 1 and 2 is associated.

Figures 5 and 6 are views similar to Figures 2, 3 and 4 illustrating theinvention yas applied to a switch and signal lever control system.

Similar reference characters refer to similar parts in each of theseveral views.

In each of the views, the contacts operated by the various relays orother devices are identied by numbers, such numbers havingdistinguishing prefixes from which they are separated by a dash when thecontacts are shown apart from the relay or other device by which theyare operated. The prefix for each of these contact numbers comprises thereference character for the respective relay or other device by whichthey are operated. For example, contact BKR- IIl shown in Figure 2 inthe circuit for energizing relay IHR is identified by the number I0separated by'a dash from the prefix 6KBl which is the referencecharacter for relay SKR, shown in Figure l, by which this contact isoperated. Similarly, contact ILR(R)-I4, also shown in the energizingcircuit for relay IHR in Figure 2, is identified by the number I4separated by a dash from the prefix ILR(R) which is the referencecharacter for the reverse solenoid ILR(R) of the route settingandlocking relay ILR shown in Figure 4.

Referring now first to Figures 1 to 4 inclusive, it will be seen that astretch of railway track is diagrammatically illustrated in Figure 1 asditions B, C and D comprise track switches as indicated at 4, 5 and 6,forming part of a number of corresponding different routes which may betraversed by traffic leaving section A. Route No. 1, as indicated by thearrow RI, is assumed to include track sections B, C, D and E in thatorder so that for this through route switches 4, 5 and 6 must be intheir normal settings. Routes Nos. 4, 5 and 6 will involve the settingof switches 4, 5 or 6 respectively to their reverse positions and eachroute is provided with a route setting and locking relay of the kindabove referred to which controls the setting of al1 the switchesassociated with the route, it being understood that each route mayinclude other switches than those indicated at 4, 5, 6 by way ofexample.

Each of the track sections A, B, C and D is shown provided with a trackcircuit including a suitable source of current, which may be a battery3, connected across the rails adjacent one end of the section, and atrack relay, designated by the reference character TR preceded by thereference character for the associated section, connected across therails adjacent the opposite end of the section.

Signal IS may govern the movement of traffic over routes Nos. 4, 5 and6, as well as over route No. 1, or separate signals may be provided foreach route or group of routes. In the specific example here consideredFigure 2 illustrates the control 0f signal IS to control traffic overNo. 1 route.

The route setting relay for No. 1 route is indicated at ILR in Figure 4,and is of the type above referred to, comprising a normal solenoid ILR(N) and a reverse solenoid ILR(R), the direct currents required forenergizing these solenoids being derive-d from the output terminals of arectifying device LRJ, the input terminals of which are connected to theterminals ABX and ANX of a source of supply of alternating current.

The route setting relay ILR is arranged to be controlled by a manuallyoperated lever or other control device indicated at ILRP in Figure 2 andhaving a normal position N and a reverse position R, and comprising acontact ILRP-20, shown in Figure 4, which is closed when the controldevice is in its normal position as indicated by the letter N adjacentthe symbol for this contact (for setting the relay ILR to its normalposition) and a contact ILRP-25 which is closed when the control deviceis in its reversed position, it being understood that in the normalposition of a route setting and locking relay the route is dissolved andis set up when the relay is in its reverse position.

The route setting and locking relay ILR in turn controls a switchsetting and locking relay for each switch in its route. The controlcircuits for switch setting relay GWR are shown, for example, in Figure4. Switch No. 6 is also included in route 6, and relay GWR is thereforealso controlled by route setting and locking relay GLR.

The signal IS for route No. l is controlled by a signal relay IHR whichcauses the signal IS to give a proceed or danger indication according towhether the relay IHR is energized or deenergized. Signal IS may be ofany suitable design, but as here shown is of the color light type,comprising a proceed lamp G and a stop lamp R. The signal relay IHR isarranged to be controlled by the manually operated control device ILRPwhich when in its normal position interrupts the energizing circuit ofthe relay IHR but when operated to its reverse position completes acircuit as shown in Figure 2 from one terminal BX of a source ofcurrent, through a contact 'I (closed when the control device ILRP is inits reverse position), contacts closed when switch indication relaysAKR, 5KB, and BKR are normally energized, front contacts 5LR(N)-I I,5LR(N)-I2 and llLR(N)-I3 closed when the route setting relays SLR, 5LB,and IILR respectively of other conflicting routes are in their normalpositions, front contact ILR(R)I4 closed when the route setting relayILR is in its reverse position, and the winding of relay IHR to theother terminal NX of the source of current. The switch indication relaysare normally energized as controlled by`pole changing contacts, such forexample as contacts I 5 and I 6 operated by switch 6 for controllingrelay BKR shown in Figure 1, when the corresponding switches 4, 5 and 6occupy their normal positions for through traiiic so that it will beevident that in order to energize the signal relay IHR to cause aproceed indication to be given when the control device ILRP is operatedfor this purpose, it is essential that the switches il, 5 and 6 shouldoccupy their normal positions, that the route setting relays SLR, BLRand ILR for conflicting routes should be in their normal or inoperativesettings and that the route setting relay ILR for the route No. 1corresponding to signal I S should be in its reverse setting.

Referring now again to Figure 4, it will be seen that the energizingcircuit of the normal solenoid ILR(N) of the route setting and lockingrelay ILR includes, in addition to the contact ILRP 2l), a back ContactIHR-I9 of the relay IHR and a front Contact ATR-Il of a track relay ATRwhich is energized when the approach section A is unoccupied by a trainor vehicle. A parallel circuit to that including the front contact ofrelay ATR includes a front Contact IANS-I8 of an approach lockingrelease relay IANS. The energizing circuit for the reverse solenoidILR(R) of the route setting relay ILR includes, in addition to thecontact ILRP-25, a series of contacts designated LR N)-2I, LR(N)22,LR(N)-Ll3, and LR(N)-24, each of which is closed only when the routesetting and locking relay of a corresponding coniiicting route is in itsnormal setting.

Referring now to Figure 3, which illustrates the energizing circuit forthe approach locking release relay IANS for route No. 1, this relay isof the slow acting type and does not, when deenergized, move to itsde-energized position until after the expiration of a predeterminedinterval of time.

The relay I ANS is provided with a pick-up circuit passing from oneterminal BX of a source of current, through contact ILR(R)25 closed onlywhen the relay ILR is in its reverse setting, a back contact ETR-21 of atrack relay BTR which is de-energized when the track section B isoccupied by a train or vehicle, and the winding of relay IANS to theother terminal NX of the source of current.

The relay IANS is also provided with a stick circuit including its ownfront contact 28 around the back contact of track relay B'IR abovereferred to.

The operation of the system above described is as follows:-

Assuming that the route setting relay ILR for route No. 1 is in itsnormal position, this route may be set up by operating the controldevice ILRP to its reverse position so as to energize the solenoid ILR Rof the relay ILR. The normal solenoid BWRQi) of switch setting relay SWRwill then become energized by its circuit passing from terminal BX,through contact DTR- El, contact 3i) of solenoid 6LR(N), contact 3| ofsolenoid ILR(R), and the normal solenoid winding 6WR(N) of relay GWR toterminal NX. The normal operating circuit for switch motor M will thenbecome closed, causing switch 6 to be moved to the` normal position ifit has previously occupied the reverse position, This circuit passesfrom terminal BX, through contact iWR(N)- 34, normal eld winding 35 ofmotor M, and armature 38 of mot-or M to terminal NX. Switches I and 5will be controlled similarly to switch E by relay ILR.

Under these conditions, the signal relay IHR will be energized providingthe track switches 4, 5 and 5 are in or operate to their normalposition. Proceed lamp G of signal IS will therefore be lighted by itscircuit including the front point of contact IHR-39.

The approach locking release relay IANS was de-energized so long as therelay ILR was in its normal position, but the pick-up circuit of therelay IANS is completed when relay ILR is in its reverse position and atrain or vehicle has entered track section B. When the relay IANS hasbeen thus picked up, the relay is maintained energized through its stickcircuit after the train or vehicle has left section B and so long asrelay ILR is in its reverse position.

The relay ILR may, however, be restored to its normal position by theoperation of the contro-l device ILRP to energize the normal solenoidILR(N) so long as the track section A is unoccupied and the signal relayIHR is de-energized.

So long, therefore, as the approach section A leading to the signal ISis unoccupied, the relay ILR may be freely set from its reverse positionto its normal position regardless of the position of the relay IANS, thestick circuit of this relay being, however, interrupted when the relayILR moves from its reverse position towards its normal position when thecontact ILRP-Zi is closed. Since, however, the relay IANS isslowreleasing, the interruption of its stick circuit does not at oncecause the relay to assume its deenergized position in which theenergizing circuit of the solenoid ILR(N) would be entirely interruptedto effect approach locking if the shunt circuit including the frontcontact of relay ATR were also broken due to the presence of a train orVehicle in track section A. Consequently, the circuit through the frontcontact of relay I ANS is maintained for a period of time suicientlylong to permit the normal solenoid ILR(N) to be energized to set therelay I LR to normal, it being understood that the completion of thiscircuit is only effected provided that the signal IS is giving a dangerindication.

In describing more in detail the control of relay ILR by relay IANS, Ishall assume that the solenoid ILR(R) of relay ILR has been energized,as previously described, by operation of the control device ILRP to itsreverse position. I shall further assume that a train then enters tra-cksection B, causing relay IANS to become energized by its pick-up circuitpreviously traced, and that a following train enters section A,deenergizing relay ATR. The circuit previously traced for solenoidILR(N) will therefore be open at contact ATR-Il. The second or parallelcircuit for solenoid ILR(N) including contact IANS-I can, however, nowbe closed if the control device I LRP is returned to its normal positionin which its Contact I LRP-20 is closed, and if relay IHR closes itsback contact IHR-I9 in response to this movement of control device ILRP.With the back contact IHR- 39 also closed, signal IS will indicate stop.

Solenoid ILR(N), upon becoming energized, will open contact ILR(R)-26 inthe circuits for relay IANS which will thereby be deenergized. RelayIANS is, however, slow releasing, and therefore its contact IANS-I 8will remain closed long enough for so-lenoid ILR(N) to complete theoperation of relay ILR and close its contact 32 in the circuit forsolenoid 6WR(R) which can be energized if solenoid 6LR(R) is thenenergized by operation of the corresponding route control device.

From the description in the Kershaw et al Patent No. 2,164,822previously referred to, it follows that contact 32 of solenoid ILR(N)will not open when this solenoid becomes deenergized, but will remainclosed until solenoid ILR(R) is again energized. Similarly, contacts ofsolenoid ILR(R) will become closed when solenoid ILR R becomesenergize-d, and will remain closed until solenoid ILR(N) becomesenergized.

After the relay IANS has eventually assumed its de-energized position,the approach locking evidently cannot be released so long as relay ATRis de-energized, that is, so long as section A is occupied.

In order to eiect the re-energization of the relay IANS, it is evidentlynecessary for the relay ILR to be again set to its reverse position soas to close the front contact ILR(R)26 (Figure 3) and for the tracksection B to be again occupied so as to close the back contact BTR-Zl ofrelay BTR.

It will thus be seen that when once the ap proach locking has beenestablished by the deenergization of the relays ATR and IANS, thislocking can only be again released by the setting of the relay ILR toits reverse position and the passage of a train or Vehicle into tracksection B. Furthermore, the de-energization and release of relay IANSdue to current failure in either its pick-up or stick circuit willprevent the release of the approach locking, thus ensuring safety inoperation under all conditions.

In Figures and 6, the invention is illustrated as applied to a system inwhich the control of the switches and signals of a route is eiected bycorresponding point and signal levers in the wellknown manner.

As shown in Figure 5, the energizing circuit of the signal relay IHR forthe signal IS of route No. 1, includes signal lever contact 43, closedwhen the signal lever is moved to its reverse position, and contacts 42,4 I, and 40 on the individual switch levers controlling track switches6, 5 and 4, these contacts being closed only when the correspondingswitch levers are all in their normal positions.

The control of the energizing circuit for the approach locking releaserelay IANS is effected by a contact indicated as 44 on the route orsignal lever IL, which is closed when this lever is in its reverseposition and is maintained closed until the lever, when moved away fromits reverse position towards its normal position, has cleared thelocking mechanism controlled by the approach locking release relay IANS. This relay need thus not be slow-acting as it is not deenergizeduntil the route or signal lever has moved beyond the position at whichthe locking mechanism is operative to prevent its movement to normal.

As shown in Figure 6, a back locking mechanism K is arranged to beprovided for the signal or route lever, the releasing coil 5I for thislocku ing mechanism being energized through a circuit including acontact 50 of the lever, front contacts ATR-49 and 48 of relays ATR andIANS and a back contact IHR-ll of the signal relay IHR. A lockingsegment 5 is mechanically connected with lever IL so that when lever ILis moved to its reverse position, segment 54 moves toward the right, andlocking dog 52 drops down off of the projection 53 of segment 54. Whenlever IL is returned toward its normal position, dog 52 in its loweredposition will engage the projection 53, thereby arresting the movementof lever IL at its indication position B until the releasing coil 5Ibecomes energized and lifts dog 52 out of engagement with projection 53of segment 54. The lever can thus only be restored to its normalposition provided that the track section A is unoccupied or that therelay EANS is energized.

Lever IL can be mechanically interlocked with switch levers LiL, 5L and6L, as indicated by the dash line 5l in Figure 5, so that when lever ILis moved t0 its reverse position R, levers 4L, 5L and 6L are locked intheir normal positions and cannot be reversed until lever IL has beenreturned past its indication position B. Switch setting relay EWR can becontrolled by lever 6L and by track relay DTR as shown in Figure 6.

The invention is evidently not limited to the particular arrangementsand connections above described and illustrated by way of example, whichmay be modified in various respects in order to meet particularconditions.

Having now particularly described my invention, I declare that what Iclaim and desire to secure by Letters Patent is:

1. In a control system for a stretch of railway track including a trackswitch, including a signal controlled by a manual control deviceindependently of occupancy of said stretch of track by a train forgoverning trallc movements over a route containing said track switch,and provided with approach locking means for preventing an operation ofsaid switch if an approach section for said signal is occupied by atrain and if. said manual control device has been put into condition forclearing said signal, the combination comprising a normally de-energizedapproach locking release relay, means controlled by said approachlocking release relay when in the energized condition for nullifyingsaid approach locking means, and means responsive to said manual controldevice if put in condition for clearing said signal and to occupancy ofsaidY stretch of track beyond said signal for energizing said approachlocking release relay while said signal is in the clear condition.

2. In a control system for a stretch of railway track including a trackswitch, including a signal controlled by a manual control deviceindependently of occupancy of said stretch of track by a train forgoverning trai-lic movements over a route containing said track switchin a given position, and including a route setting and locking relaycomprising a normal solenoid which upon becoming energized eiects acondition required for operation of said switch to the opposite positionand also comprising a reverse solenoid which when energized eiiects acondition required for operation `of said switch to rsaid given positionand said route setting and locking relay remaining locked in theposition to which itv was last set until its opposite solenoid isenergized, the combination comprising a normally de-energized approachlocking release relay, means responsive to said manual control device ifput in condition for clearing said signal and4 responsive to occupancyoi said route beyond said signal for energizing said approach lockingrelease relay while said signal is in the clear condition, and a frontcont-act of said approach locking release relay included in a circuitfor energizing said normal solenoid in multiple with a contact which isclosed only if an approach track section for said signal is unoccupied.

3. In a control system for a stretch of railway track including a trackswitch, including a signal controlled by a manual control deviceindependently of occupancy of said stretch of track by a train forgoverning traic movements over a route containing said track switch in agiven position, and including a route setting and locking relaycomprising a normal solenoid which upon becoming energized effects acondition required for operation of said switch to the opposite positionand also comprising a reverse solenoid which when energized effects acondition required for operation of said switch to said given positionand said route setting and locking relay remaining locked in theposition to which it was last set until its opposite solenoid isenergized, the combination comprising a normally de-energized approachlocking release relay, a pick-up circuit for energizing said approachlocking release relay closed by said route setting relay in the reverseposition and by the occupied condition of said stretch of track beyondsaid signal, a stick circuit closed by said route setting relay in thereverse position for retaining said approach locking release relayenergized, and a front contact of said approach locking release relayincluded in an energizing circuit for said normal solenoid in multiplewith a contact which is closed only if an approach track section forsaid signal is unoccupied.

4. In a control system for a stretch of railway track including a trackswitch, including a signal controlled by a manual control deviceindependently of occupancy of said stretch of track by a train forgoverning traic movements over a route containing said track switch in agiven position, and including a route setting and locking relaycomprising a normal solenoid which upon becomlng energized effects acondition required for operation of said switch to the opposite positionand also comprising a reverse solenoid which when energized eiects acondition required for operation of said switch to said given positionand said route setting and locking relay remaining locked in theposition to which it was last set until its opposite solenoid isenergized, the combination comprising a normally de-energized slowrelease approach locking release relay, means responsive to said manualcontrol device if put in condition for clearing said signal andresponsive to the occupied condition of said route beyond said signalfor energizing said approach locking release relay, and a front contactof said approach locking release relay included in an energizing circuitfor said normal solenoid in multiple with a contact which is closed onlyif an approach track section for said signal is unoccupied.

5. In a control system for a stretch of railway track including a trackswitch and a signal for governing trailic movements over said switch,including mechanically interlocked levers for effecting operations ofsaid switch and clearing said signal, including approach locking meansfor arresting movement of the signal lever at a given indicationposition if said signal lever is returned from a reverse position forclearing said signal toward a normal position while an approach sectionfor said signal is occupied, 'the combination comprising an approachlocking release relay, a Contact operated by said signal lever closedwhile said signal lever is in its said reverse or said indicationposition or in any other position between these two positions, meanseffective while said signal is in the clear condition for energizingsaid approach locking release relay including said contact Aof saidsignal lever and controlled by the occupied condition of said stretch oftrack ahead of said signal, and means comprising a front contact of saidapproach locking release relay for releasing said approach lockingmeans.

6. In a control system for a stretch of railway track including a trackswitch and a signal for governing traffic movements over said switch,including mechanically interlocked levers for eiTecting operations ofsaid switch and clearing said signal, including an electric lock whichwhen fle-energized arrests movement of the signal lever at a givenindication point when said lever is being returned to a normal positionfrom a reverse position to which it has been moved for clearing saidsignal, the combination comprising an approach locking release relay, apick-up circuit controlled by said signal lever" when operated to saidreverse position and by the occupied condition of said stretch of trackbeyond said signal for energizing said approach locking release relay, astick circuit independent of track occupancy controlled by said signallever for retaining said approach locking release relay energized untilsaid signal lever is moved beyond said given indication point toward itsnormal position, and a circuit including a front contact of saidapproach locking release relay in multiple with a contact which isclosed only if an approach section for said signal is unoccupied forenergizing said electric lock.

7. In a control system for a stretch of railway track capable ofarrangement into a plurality of routes and having signal means forgoverning traic movements over each of said routes, including manuallycontrollable route means for arranging each of said routes, andincluding approach locking means for retaining each route as arranged bythe corresponding manually controllable route means if an approach tracksection for its signal means is occupied by a train, the combinationcomprising a normally de-energized approach locking release device for agiven route, a circuit for energizing said approach locking releasedevice while said signal is in the clear condition closed at one pointby the route control means for said given route when in condition 1 orarranging said given route and closed at another point by a contactwhich is closed when said given route is occupied by a train, and meanscomprising said approach locking release device in its energizedcondition for nullifying the approach locking means for said givenroute.

8. In a control system for a stretch of railway track including trackswitching means for arranging a plurality of routes over said stretch,I

including manually controllable means for effecting operation of saidtrack switching means for arranging each of said routes, and includingapproach locking means for rendering said manually controllable meansineffective to ope-rate said switching means for each route if anapproach track section for the corresponding route is occupied by atrain, the combination comprising a normally de-energized approachlocking release device for a given route, a circuit for energizing saidapproach locking release device closed by said manually controllablemeans when in condition for eiecting arrangement of said given route andby a Contact which is closed if said given route is occupied by a train,a stick circuit controlled by said manually controllable means forretaining said approach locking release device energized While saidsignal is in the clear condition, and means controlled by said approachlocking release device in the energized condition for nullifying theapproach locking means for 10 said given route.

CHARLES FRANCIS DICKSON VENNING.

